<template lang="">
<div class="pagination">
    <!-- 上 -->
    <button :disabled='pageNo==1' @click='$emit("getPageNo",pageNo-1)'>上一页</button>
    <button v-if='startNumberAndEndNumber.start>1' @click='$emit("getPageNo",1)' :class='{active:pageNo==1}'>1</button>
    <button v-if='startNumberAndEndNumber.start>2'>···</button>

    <!-- 中 -->
    <button v-for="(page, index) in startNumberAndEndNumber.end" :key="index" v-if='page>=startNumberAndEndNumber.start' @click='$emit("getPageNo",page)' 
      :class='{active:pageNo==page}'>{{page}}</button>
    
    <!-- 下 -->
    <button v-if='startNumberAndEndNumber.end<(totalPage-1)'>···</button>
    <button v-if='startNumberAndEndNumber.end<totalPage' @click='$emit("getPageNo",totalPage)' :class='{actve:pageNo==totalPage}'>{{totalPage}}</button>
    <button :disabled='pageNo==totalPage' @click='$emit("getPageNo",pageNo+1)'>下一页</button>
    
    <button style="margin-left: 30px">共 {{total}} 条</button>
  </div>
</template>
<script>
export default {
  name: "Pagination",
  props: ["pageNo", "pageSize", "total", "continues"],
  computed: {
    //总共多少页
    totalPage() {
      return Math.ceil(this.total / this.pageSize);
    },
    //计算出起始页码和结束页码【连续页码的数字：至少是5】
    startNumberAndEndNumber() {
      const { continues, pageNo, totalPage } = this;
      //先定义两个变量 存储起始数字和结束数字
      let start = 0,
        end = 0;
      //连续页码数字5【至少5页】，如果页码不够5页
      if (continues > totalPage) {
        start = 1;
        end = totalPage;
      } else {
        //正常现象【总页码＞5】
        start = pageNo - parseInt(continues / 2);
        end = pageNo + parseInt(continues / 2);
        //start出现0或者负数
        if (start < 1) {
          start = 1;
          end = continues;
        }
        //end大于页码数
        if (end > totalPage) {
          end = totalPage;
          start = totalPage - continues + 1;
        }
      }
      return { start, end };
    },
  },
};
</script>
<style lang="less">
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
</style>